1. Field of the Invention
The present invention relates to a bleaching detergent composition showing excellent performance for both the detergency against sebum dirt stains and that against lipophilic dirt stains, such as yellowish stains of underwear. In the present invention, the term "yellowish stains" used herein refers to a color change of white underwears to yellowish color by deposition and accumulation of excreta.
2. Discussion of the Related Art
Conventionally, various proposals have been made to improve detergency against yellowish stains caused by detergent compositions by formulating bleaching agent components to the detergent compositions.
For example, Japanese Patent Laid-Open Nos. 59-22999 and 6-316700 disclose bleaching agent compositions and bleaching detergent compositions, each containing an organic peracid precursor which produces an organic peracid having an alkyl group with a particular number of carbon atoms, and a hydrogen peroxide releasing material. The organic peracids produced from the organic peracid precursors mentioned above show remarkably excellent bleaching power against dirt stains, but in cases where the organic peracid precursors are added to ordinary detergent compositions to make bleaching detergent compositions, sufficiently good bleaching effects cannot be obtained. The reasons therefor are presumably as follows: Since the surfactant concentration, particularly a nonionic surfactant concentration, is very high in these detergent compositions, the organic peracid precursors are enclosed in the surfactant micelle and dissolved therein. Therefore, the reaction of the organic peracid precursors with the hydrogen peroxide releasing material is notably inhibited, thereby preventing the generation of organic peracids, which are bleaching species. Higher the proportion of the nonionic surfactants in the surfactant components, more notable the inhibition of the reaction of the organic peracid precursors with the hydrogen peroxide releasing material becomes. For the reasons given above, the formulation of the nonionic surfactants in an effective amount has been difficult, when compared with anionic surfactants, thereby making it impossible to satisfy both the detergency against the sebum dirt stains and the detergency against the yellowish stains of underwear.
On the other hand, the present inventors have found that a high detergency can be performed against the sebum dirt stains even when the concentration of the surfactant used is notably reduced by using a crystalline alkali metal silicate having an alkaline capacity in a high concentration and improving metal ion capturing ability. However, in this washing method, a sufficient washing performance against the lipophilic dirt stains, such as yellowish dirt stains on underwear, cannot be achieved.
Examples of detergent compositions where a crystalline silicate and a bleaching component are essential components include Japanese Patent Laid-Open Nos. 6-116591 and 7-53992. The above publications pertains to bleaching detergents comprising sodium crystalline silicates, surfactants, and bleaching components comprising bleaching activating agents which produce peroxy fatty acids and sodium percarbonate. The bleaching detergents having compositions disclosed in these references have insufficient detergency against the sebum dirt stains. In addition, since the compositional ratio of the surfactants are high, the composition does not allow to effectively produce organic peracids by the bleaching activating agents (organic peracid precursors). Therefore, sufficient effects in removing lipophilic dirt stains, such as yellowish dirt stains on underwear, cannot be obtained.